dovecot - Apr 2010 - Again: Occasional problem with POP3-Download

Hello everyone,

in february I posted the mail below[1].

I can now reproduce the problem. When filling up a mailbox with postfix'
smtp-source with dozens of identical mails, then it is never possible
for me to fetch one single mail out of the mailbox. The process of
fetching mail via POP3 always fails. It makes no difference which mail
client I use. I have tested KMail, Outlook and Thunderbird.

Can anyone confirm this? Is dovecot for some reason unable to deliver
such identical mails?

Can it be the case that this is a problem with too similar message ids?

~/Maildir/cur$ cat * | grep -i message-id
Message-Id: <1024.0003.0008 at alphamobil>
Message-Id: <1024.0003.0009 at alphamobil>
Message-Id: <1024.0003.0006 at alphamobil>
Message-Id: <1024.0003.0007 at alphamobil>
Message-Id: <1024.0003.0005 at alphamobil>
Message-Id: <1024.0003.0004 at alphamobil>
Message-Id: <1024.0003.0003 at alphamobil>
Message-Id: <1024.0003.0002 at alphamobil>
Message-Id: <1024.0003.0001 at alphamobil>
Message-Id: <1024.0003.0000 at alphamobil>

Thanks and greetings from Munich!
AT




[1]
Hello everyone,

I have two mailservers [1] running dovecot. Mail store format is
maildir. Every once in a while I have the following problem: When a User
downloads his mail via POP3, the client says something like "the server
has closed the connection unexpectedly, and gives this reason:
[...blahblah...]". 

One can now cancel the download, and restart it, and the problem shows
up again and again. The first few mails get downloaded, and then the
process stops.

Strange to say the "blahblah"-portion is a piece of text out of the
email that doesn't want to get downloaded. 

Then I remove this single message out of the Maildir/cur-directory, and
everything is fine again.  It is easy to figure out which mail to delete
because it's the first one that is not market as seen

	[...]
	filename...:2,S
	otherfilename...;2,   <= this file must be deleted
	[...]


For me it looks as if dovecot had a problem with some byte sequence in
this mail, and for some reason it gives an error message to the client
which is taken out of the mail.

On the SuSE-Machine, before dovecot there was a courier-imapd running,
which never showed this kind of problem, so it should not be a client
problem.

Hopefully my description is clear enough. 

Does anyone have an idea what's going on here?


Thanks.
Andre



[1]
One machine is a openSuSE 11.2 with 

# rpm -qa | grep dovecot
dovecot12-backend-sqlite-1.2.9-0.1.1.i586
dovecot12-backend-mysql-1.2.9-0.1.1.i586
dovecot12-backend-pgsql-1.2.9-0.1.1.i586
dovecot12-1.2.9-0.1.1.i586

The other machine is a Debian Lenny with

# dpkg -l | grep dovecot                                                 
dovecot-common 1:1.0.15-2.3+lenny1
dovecot-imapd  1:1.0.15-2.3+lenny1
dovecot-pop3d  1:1.0.15-2.3+lenny1

-- 
Andre Tann

On Wed, 2010-04-28 at 16:01 +0200, Andre Tann wrote:
> I can now reproduce the problem. When filling up a mailbox with
postfix'
> smtp-source with dozens of identical mails, then it is never possible
> for me to fetch one single mail out of the mailbox. The process of
> fetching mail via POP3 always fails. It makes no difference which mail
> client I use. I have tested KMail, Outlook and Thunderbird.
What about talking POP3 protocol directly?

telnet pop3.server.org 110
user foo
pass bar
uidl
retr 1
retr 2
retr 3
quit

Does that work? (Try from the client machine first, and if that doesn't
work try again from localhost.)
> Can anyone confirm this? Is dovecot for some reason unable to deliver
> such identical mails?
No. But what do you have in pop3_uidl_format?

If POP3 UIDLs differ, I think it's unlikely the problem is with Dovecot
itself (but instead with some anti-virus/firewall/whatever in the
middle).
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Timo Sirainen, Donnerstag 29 April 2010: 
> What about talking POP3 protocol directly?
> 
> telnet pop3.server.org 110
> user foo
> pass bar
> uidl
> retr 1
> retr 2
> retr 3
> quit
Hm, I can't try that by hand, because in fact I only offer POP3s via
Port 995 to the world: 

mail:~# grep -i ^protocols /etc/dovecot/dovecot.conf
protocols = pop3s imap imaps

IMAP on port 143 is neccessary to allow access to squirrelmail, and is
hidden by the packet filter from the world.


> No. But what do you have in pop3_uidl_format?
> 
> If POP3 UIDLs differ, I think it's unlikely the problem is with Dovecot
> itself (but instead with some anti-virus/firewall/whatever in the
> middle).
There is no Firewall or Antivirus-Code in the middle, or to be more
precise: I have tried to download from a linux box, where no firewall
and no virus killer is running on. The result is the same, as if I
download it from a Windows XP box, where firewall and virus killer is
running.

mail:~# grep uidl /etc/dovecot/dovecot.conf
  #pop3_reuse_xuidl = no
  pop3_uidl_format = %08Xu%08Xv

Is that OK?


AT

-- 
Andre Tann